1. Field of the Invention
The present invention relates to a sheet processing apparatus capable of binding in a plurality of spots of a sheet bundle by conveying the sheet bundle with alignment property maintained, and, to a sheet processing apparatus used in an image forming apparatus, for example, such as a printer, a copying machine or the like.
2. Description of the Prior Art
In a conventional sheet-bundle binding apparatus, a binding mechanical section is moved along a sheet bundle aligned on a stacking tray as a sheet stacking portion so that an arbitrary position of a sheet end portion is to be bound. For example, as a sheet-bundle binding apparatus provided in an image forming apparatus such as a copying machine or the like, some have such a structure in which, after a sheet on which a toner image is recorded by an image forming section is conveyed to a stacking tray where a predetermined number of sheets is aligned, a binding mechanical section is moved to a predetermined position of an end portion of the sheet bundle thus aligned on the stacking tray to perform the binding process.
This sheet-bundle binding apparatus, however, is required to move the binding mechanical section by a distance corresponding to various sizes of sheets, since an arbitrary position of the end portion of the sheet bundle is to be bound. This results in not only that a structure of the sheet-bundle binding apparatus becomes complicated, but also that a rate of breakdown occurrence becomes higher due to the movement of the binding mechanical section. In addition, a space for moving the binding mechanical section is required, so miniaturization of the apparatus becomes difficult. As a result, the conventional sheet-bundle binding apparatus has such problems as that manufacturing at a lower cost is difficult, and that a broader area is required for installing the image forming apparatus including the sheet-bundle binding apparatus.
In order to solve such problems, there has been proposed an apparatus in which a binding mechanical section is fixed and a sheet bundle is conveyed to a predetermined position with respect to the binding mechanical section, thereby capable of performing the similar binding process of the sheet bundle. This apparatus can make the structure of the binding mechanical section simple and make the rate of breakdown occurrence of the binding mechanical section lower.
In the foregoing conventional apparatus, however, it is required to move the aligned sheet bundle for performing the binding process, and therefore alignment property becomes deteriorated during the conveyance of the sheet bundle, so there is a problem that alignability of the sheet bundle is lower when compared with the alignability of such a type of an apparatus where the binding mechanical section is moved.
Thus, the present invention has been accomplished to solve the aforementioned problems, and it is an object of the present invention to provide a sheet processing apparatus capable of preventing deterioration of alignment property during conveyance of a sheet bundle which has been aligned but before subjected to a binding process and capable of binding the sheet bundle with high alignability.
In a sheet processing apparatus including, as a representative structure of the present invention to accomplish the above object, a stacking portion for stacking a plurality of sheets to be made as a sheet bundle, an alignment reference wall extending in approximately parallel with a conveying direction of the sheet bundle on one side of side surfaces of the sheet bundle, a processing mechanical section for treating an aligned sheet bundle, and a plurality of rotating body pairs disposed in a direction approximately perpendicular to the conveying direction of the sheet bundle for conveying the sheet bundle in a pinching manner, it is characterized in that the rotating body pairs have different pressures for pinching the sheet bundle.
According to the present invention, as mentioned above, since it is so structured that each of the plural rotating means pairs arranged in a widthwise direction perpendicular to a sheet conveying direction has a pressure different from that of other rotating means pairs for respectively pinching a sheet bundle, and more specifically that, as a rotating means pair is disposed nearer an alignment reference wall, the roller pair has a higher pressure for pinching the sheet bundle, a sheet bundle before subjected to the binding process, at the time of being conveyed, can be conveyed as being pressed with respect to the alignment reference wall, with the result that the aligned sheet bundle can be conveyed with the aligned state maintained. Thus, the sheet bundle can certainly conveyed without disordering the alignment property of the sheet, and also processes such as binding or the like can be performed without disordering the alignment.
Thus, since the alignment property of the sheet bundle is maintained, a mechanism for moving a stapler unit and the space for the mechanism, which have been conventionally required, can be omitted, thereby realizing a simplification of the apparatus as a whole and reductions in cost, installation space, and power consumption.
More specifically, it is characterized in that, for example, with respect to the plural roller pairs disposed, as a roller pair is disposed nearer the side of the alignment reference wall, the roller pair has a higher pressure for pinching the sheet.
According to the above structure, at the time of conveying a sheet bundle, which has been aligned but not subjected to the binding process, the sheet bundle is conveyed as being pressed with respect to the alignment reference wall, and consequently, this can lower the deterioration of the alignability which is caused at the time of conveying the sheet bundle.